Shock resistant spark plug



June 22, 1954 M. D. HAyyQR'rH 2,682,017

SHOCK RESISTANT SPARK PLUG Filed Noy'grz, 1952 Fig. 3. /2 66 "8`T4 62 www Patented June 22, 1954 SHOCK. RESISTANT SPARK PLUG Merton D. Haworth, Fanwood, N. J., assignor, by mesne assignments, to the United States of America Application November 12. 1952, ISerial No. 319,807

5 Claims.

The invention relates generally to spark plugs and particularly to those which are subjected to a substantial amount of shock due to impact, vibration or other factors. In certain devices which employ spark plugs that are subjected to a substantial amount of shock, the problem of failure of the spark plugs due to fracturing of the porcelain insulator is very real. A specific example of a device of this type is the mechanized, military flame thrower. The mechanized flame thrower is mounted on a tank or other military vehicle, and under field conditions of use is subjected to shock due to the impact of ammunition .on any part of the tank or vehicle, and to road shock. The flame throwers include an igniter spark plug in their ignition chamber which ignites the flame producing material. Failure of theA spark plug incapacitates the entire flame thrower and consequently constitutes a serious problem.

It is an object of this invention to provide a spark plug which is satisfactorily shock resistant to the conditions existing in the eld use of mechanized, military flame throwers and in other devices subjected to substantial shock.

It is another object of this invention to provide a shock resistant spark plug which may be used interchangeably with conventional spark plugs and therefore precludes the necessity for any change or adaptation in existing equipment in converting from the old to the new plugs.

It is a specic object of this invention to provide a resiliently mounted, shock resistant, spark plug for a mechanized, military, ilame thrower which can withstand the ballistic and road shock of the vehicle carrying the flame thrower operating under eld conditions.

It is a further object of this invention to provide a shock resistant spark plug which is: made of non-corrosive materials; substantially unaffected by temperature and humidity variations; suitable for mass production; easily installed and maintained; and which satisfies the electrical requirements of a high tension, ignition circuit.

These and other objects will become apparent from the following description and claims take-n in conjunction with the drawings wherein:

Fig. 1 is a longitudinal, sectional view of the forward portion of a flame thrower barrel.

Fig. 2 is a front, elevationa1 view of the flame thrower barrel shown in Fig. 1.

Fig. 3 is a sectional view taken on line 3-3 of Fig. 4. y

Fig. 4 is a sectional view taken on line 4 4 of Fig. 3.

Fig. 1 shows the forward portion of a llame thrower barrel and particularly shows the structure which constitutes the ignition chamber. The ignition chamber designated generally by reference numeral IIJ is the part of the flame thrower where the name producing material and the igniting material contact each other, and are ignited byv sparks caused by one or more igniting spark plugs. This invention relates primarily to the spark plugs I2 which create the sparks which ignite the materials in the ignition chamber.

The ignition chamber I0 is formed by the forward portion of cylindrical flame thrower barrel I4 and the ignition chamber wall I6, which is positioned within and secured to said barrel. Wall I6 has a central opening I8 formed therein which receives the llame producing material barrel 20 and maintains it concentrically within and spaced from the flame thrower barrel I 4. As can be seen in Fig. l, the forward end of barrel 20 is beveled at 22 to facilitate ejection of the flame producing material out of said barrel. The rearward end of barrel 20 communicates with a conventional source of llame producing material (not shown). yIgnition chamber wall I6 has two threaded openings 24 and 26 formed therein, each of which is adapted to receive the externally threaded collar of a spark plug. Wall I6 has two additional openings which receive and position igniting material nozzles 28 and 30, which are in communication through appropriate piping with a source of igniting material (not shown). The relative positions of the spark plugs and nozzles in the ignition chamber wall 'I6 can be best seen in Fig. 2. Flame thrower barrel I4 has air vents 32 and 34 formed therein, and at its forward end it supports fixed, grounded electrodes 36 and 38.

A11 of the structure described above is substantially conventional llame thrower structure and constitutes the prior art setting for the prior art spark plugs. Very briefly, the prior art spark plugs comprise a central electrode which is surrounded by along, cylindrical, porcelain insulator having an integral flange formed thereon which is adapted to be surrounded by a crimped metal collar. This collar is externally threaded on one side of its ends and is adapted to be rigidly attached to the wall I6 in one of the openings 24 and 26.

As was previously stated, the prior art arrangement was defective in that the rigid attachment of the spark plug to the ignition chamber wall I6 permitted ballistic, road and other shocks to be transmitted through the flame thrower-barrel, ignition chamber wall, and spark plug collar to the porcelain insulators. In a large number of cases this caused fracturing of the insulators and resulted in the spark plugs failing, thereby incapacitating the entire name thrower. My invention resides in providing a novel spark plug which eliminates this serious defect.

Referring particularly to Figs. 3 and 4, the im.- proved spark plug comprises 'conventional Nichrome wire electrode 4B which is adjustably mounted in porcelain insulator 42. Threaded end 43 of electrode 40 is adjustably received within threaded opening 44 formed in insulator 42, and is adapted to contact the terminal end 48 of electrical current conductor 5D. Terminal end 48 is positioned in connector 4E which is secured to threaded end 43 and appropriately insulated as by insulating jacket 52. Electrode 40 may be adjusted to vary the amount thereof which projects out of the insulator 42 to thereby vary the distance between itseli and its associated, grounded electrode, and can be locked in any adjusted position by lock nut 54 which is made of an insulating material. Porcelain insulator 42 has a centrally located flange 56 formed thereon which is adapted to be surrounded by soft steel collar E3 which may be crimped thereon or molded thereabout. Externally threaded mounting nut S56 is positioned concentrically about and spaced from insulator 42. As can be clearly seen from Fig. 3, mounting nut 60 has an aperture 62 `which has an internal diameter in excess of the external diameter of insulator 42 which thereby provides an annular space between the insulator and the mounting nut. Collar` 58 is connected to nut Gil by three flexible spring fingers 64. Each spring finger B4 is electrically spot welded to the collar 58 and the nut 60 at points 66 and 6B respectively (see Fig. 3). Electrical spot welding makes it possible to effect an adequate joint between the flexible spring fingers and the parts to which they are secured without destroying the resilience of said spring lingers.

As can be seen in Figs. 1 and 2, the spark plugs l2 are mounted in the openings 24 and 26 in the ignition chamber wall IB. The iiexible connection between the electrode and insulator carrying collar 5B and the mounting nut 60 of each spark plug substantially prevents any shock which might be imparted 'to the llame thrower from being transmitted to the insulator 42. In this regard it should be noted that insulator 42 is free to move within aperture G2 relative to nut 60.

The events which transpire in the ignition chamber Hl are the following: A flame producing material such as a jellied gasoline is ejected out of the barrel 2@ into the ignition chamber I0 by actuation of the appropriate trigger on the flame thrower. An igniting mixture of gases is sprayed out of the nozzles 28 and 30 rinto the ignition chamber Il! simultaneously. By actuation of another trigger, a spark is caused between the tip of the electrode 40 of each of the spark plugs l2 and their respective, associated, grounded electrodes 36 or 38. The sparks ignite the gas mixture which in turn ignites the jellied gasoline.

Having described one specific embodiment of my invention, Ido not thereby intend to limit myself to the precise arrangement disclosed but intend to include all equivalent structure which falls within the spirit of the invention and the scope of the appended claims.

I claim:

1. In a mechanized military flame thrower having a main barrel, a wall secured in said barrel thereby establishing an open ended ignition chamber, means for introducing a llame-producing material into said ignition chamber, means for introducing an igniting material into said ignition chamber, and means for causing a spark in `said ignition chamber, the improvement in said means for causing a spark comprising a resiliently mounted spark plug. y

2. A device as dened in claim l wherein said spark plug includes an electrode, an insulating jacket surrounding said electrode, a collar surrounding said jacket, a` nut adapted to be secured in said wall, and a flexible finger connecting vsaid collar and said nut.

3. A. device as defined in claim 2 wherein lsaid nut is apertured, and is positioned concentrically about and spaced from said jacket.

4. A shock resistant spark plug comprising, an externally threaded metallic mounting nut having a longitudinal internal aperture an elon-` gated insulator extending through said aperture and beyond said nut, the exterior diameter of the portion of said insulator lying within said aperture being substantially less than the diameter of said aperture, said insulator being formed with an integral flange exterior of `and spaced from said nut, a metallic collar formed about said flange and having an external dimension substantially the same as an external dimension of said nut, a plurality of narrow elon gated spring strips joining said collar with said nut at points of equal dimension, andan electrede extending longitudinally through said insulator.

5. A spark plug as dened in claim 4- wherein said'nut and said collar are formed with a vplu-- rality of flat exterior surfaces and wherein said spring strips are 'fiat and spot welded to said flat exterior surfaces.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date ,980,566 Schmidt Jan. 13, 19.11 2,311,601 Slaght Feb. 16, 1943 

